Yes, you’ll still need to use a regulator if the rest of your project is running at 5V, but if the pins are 5V tolerant, interfacing the ESP8266 with a variety of hardware becomes very easy.

By flashing the esp-link firmware into your ESP8266, you talk directly to the microcontroller over WiFi as if it were connected by a serial cable: the ESP8266 becomes a totally transparent WiFi ...